Familial cortical myoclonic tremor with epilepsy (FCMTE) is an autosomal inherited disease mainly characterized by adult-onset cortical myoclonus and infrequent epilepsy. Over the past a few decades, we have used a number of genomic technologies to examine its genetic etiology but failed to identify likely pathogenic mutations. In the current study, we used long-read sequencing (LRS) on the PacBio Sequel platform and the Oxford Nanopore platform, and identified pentanucleotide repeat expansions within the SAMD12 gene as a major genetic etiological factor in FCMTE, corroborating a recently published study in Japan. Our study suggested that LRS is an effective tool for molecular diagnosis of genetic disorders caused by complex genomic variants that cannot be examined by conventional short-read exome and genome sequencing techniques. (By Dr. Sheng Zeng, https://jmg.bmj.com/content/early/2018/09/07/jmedgenet-2018-105484 )